Various batteries, for example lithium secondary batteries such as lithium ion batteries, chemical cells such as nickel hydrogen secondary batteries, and physical cells such as electric double layer capacitors, are used as power sources installed in vehicles that use electricity as a drive source, personal computers, and other electrical products. A battery in which a predetermined electrode body unit and an electrolyte are sealed into the interior of a metal case may be cited as a typical example of this type of battery.
The battery case used in this type of battery may take various shapes, but in the case of a battery installed in a vehicle, for example, a shape that permits a large number of batteries to be arranged neatly so as to make efficient use of limited space is preferable, and an angular case having a flat rectangular shape that corresponds to an electrode body unit having a flat shape such as a wound shape or a stacked shape so as to be able to house the electrode body unit may be cited as a typical example thereof.
This type of battery is assembled by housing a predetermined electrode body unit in a case (case main body), attaching a predetermined sealing plate (in other words, a lid member for closing an opening portion of the case; likewise hereafter) to the opening portion of the case (in other words, a housing opening for housing the electrode body unit; likewise hereafter), and then welding the sealing plate to a peripheral edge of the opening portion to seal the case opening portion. Patent Document 1 describes a technique of welding a sealing plate to the peripheral edge of a case opening portion of an angular case main body efficiently as a related art technique. Patent Document 2 describes a sealing plate used to seal an opening portion of a battery case, which is structured such that a projecting portion is formed in the vicinity of a safety valve formed on a thin film.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-195490
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2006-351234